1. Field of the Invention
The present invention relates to a dielectric line used in an extremely high frequency (EHF) band and/or in a microwave band, a high frequency circuit and a high frequency circuit apparatus.
2. Description of the Related Art
Conventionally, a waveguide, a dielectric line, a flat circuit type transmission path and so on are used as a transmission path for signals in a microwave band and/or in an EHF band. These transmission paths are used properly in accordance with a circuit construction, a characteristic required for a given circuit, a purpose of a given circuit apparatus and so on.
Japanese Unexamined Patent Application Publication No. 2000-134008 discloses components of a dielectric-installed waveguide.
In general, a design parameter for constructing a high frequency module having a rectangular waveguide as a transmission path only depends on horizontal and vertical dimensions of a section of a waveguide. Therefore, the design has low flexibility.
A specific dielectric constant of a dielectric installed as a waveguide may be used as a design parameter among components of a dielectric-installed waveguide of conventional dielectric lines. Thus, a higher design flexibility can be obtained compared to that of a hollow waveguide.
A conventionally designed dielectric-installed waveguide has a groove facing against two upper and lower conductors. The two upper and lower conductors are aligned such that a sectionally rectangular dielectric strip can fit in the groove.
However, the sectionally rectangular groove cannot easily be formed on a metal plate. The variation in characteristic due to the precision of the dimensions of the groove and the dielectric strip cannot be reduced. In addition, since line expansion coefficients differ greatly between a conductive plate and the dielectric strip, a characteristic may change due to the deformation of the dielectric strip where there is a change in environmental temperature. When chipping or cracking occurs in the dielectric strip, the characteristic is also changed.
The object of the present invention is to provide a dielectric line, which can be easily manufactured and suppresses a variation in electric characteristics and a change in characteristics due to a change in temperature, as well as a high frequency circuit and a high frequency circuit apparatus having the dielectric line.
According to one aspect of the invention, there is provided a dielectric line including two conductors and a dielectric strip provided between the two conductors. In this case, the two conductors have respective grooves between which the dielectric strip fits. The bottom corner of the groove has a cross-sectional radius form. The side surface of the groove tapers such that the width of the groove can increase as a distance from the bottom surface increases. A gap is provided between the side surface of the groove and the side surface of the dielectric strip.
A gap may be provided between the bottom surface of the groove and a surface of the dielectric strip facing against the bottom surface of the groove.
Preferably, an opening edge of the groove has a cross-sectional radius form or a cross-sectional chamfered form.
The two conductors may be symmetric with respect to a plane.
A corner of the dielectric strip may have a cross-sectional radius form.
Preferably, the width of the groove is equal to or less than xc2xd of a wavelength in an operating frequency band or below. Twice the value of the groove depth may be equal to or greater than xc2xd of the wavelength in the operating frequency band, and may be equal to or less than the wavelength.
The two conductors may have different rigidity.
Preferably, the thickness of a connection portion of the two conductors is different from each other such that the two conductors can have the different rigidity.
According to another aspect of the present invention, there is provided a high frequency circuit comprising a dielectric line having one of the above-described constructions as a signal transmission line.
According to another aspect of the present invention, there is provided a high frequency circuit apparatus including a high frequency circuit in a portion for processing sent signals or received signals.
According to an aspect of the present invention, a conductor can be manufactured easily by die-cast molding. The dielectric strip can be fitted in the groove easily, which improves the assembly characteristic. The dielectric strip can be positioned easily at the center of a space formed between the grooves of the two conductors. The relative expansion of the dielectric strip due to the temperature increase can be absorbed by the gap between the side surface of the dielectric strip and the side surface of the groove. Therefore, stable electric characteristics can be maintained.
According to an aspect of the present invention, cracking, chipping or deformation of the dielectric strip can be prevented. Thus, the change in characteristic can be sufficiently avoided.
According to an aspect of the present invention, when a conductor is manufactured by die-cast molding, the lifespan of the die can be increased. The current concentration in the edge portion of the groove opening edge of the two conductors can be alleviated. Thus, the transmission loss can be suppressed.
According to an aspect of the present invention, symmetrical characteristic of stress to a space formed by facing grooves can be maintained when two conductors have contact. Thus, an entirely stable rigid structure can be obtained.
According to an aspect of the present invention, the bottom surface of the groove and the upper and lower surfaces of the dielectric strip have surface contact. Therefore, no unnecessary spaces occur, and the stable electric characteristic can be obtained. The dielectric strip can be inserted to the grooves of the conductors, which improves the assembly characteristic. The ease of the insertion of the dielectric strip to the grooves and the sensitivity of the wobble due to the tolerance of the width dimension of the dielectric strip can be alleviated.
According to an aspect of the present invention, the single mode transmission is possible in the used frequency band. As a result, no losses relating to mode changes occur, and lower transmission loss can be obtained.
According to an aspect of the present invention, a less rigid conductor bends in relation to a more rigid conductor. Thus, the tightness of the two conductors is increased, and the transmission loss can be suppressed.
According to an aspect of the present invention, the two conductors of the same material can have different rigidity. The increase in total manufacturing costs does not occur.
According to an aspect of the present invention, an apparatus having fewer transmission losses and higher power efficiency can be obtained. The decrease in the signal to noise ratio can be suppressed. When a radar is used, the detectable distance can be increased. When a communication apparatus is used, the data transmission error rate can be reduced.